TROON, Scotland — The feeling of invincibility in golf is fleeting, which is why players try to hang onto it for as long as they can, an attempt to strike as often as possible while the irons (and putter and woods) are hot.

If you look at the sport at its top echelon entering Thursday’s first round of the British Open at Royal Troon, you see four players having passed the torch among themselves for the last few years.

Just when it looks like one of them is about to separate himself — a la Tiger Woods during his historic run of dominance — another one of them seizes the spotlight.

In 2014, Rory McIlroy was all the rage, winning the British Open, WGC-Bridgestone and the PGA Championship in succession and finishing runner-up in the Tour Championship. McIlroy, who had 12 top-10 finishes that year, was seemingly always in contention.

At the time, it looked like McIlroy was going to hold onto the No. 1 ranking until he was 40.

Along came Jordan Spieth.

Spieth won five times in 2015, including the Masters, U.S. Open and Tour Championship. He finished tied for fourth in the British Open and his second in the PGA Championship was among four runner-up finishes that year.

At that time, it looked like Spieth was going to hold onto the No. 1 ranking until he was 40.

Enter Jason Day.

The affable Aussie began to seize the spotlight in the PGA at Whistling Straits, where he out-dueled Spieth to win his first major, then going on to win the Barclays and BMW Championships to end 2015 before winning three more times this year — at the Arnold Palmer Invitational, the WGC Match Play and the Players Championship.

At the time Day left TPC Sawgrass back in May, it looked like he would hold onto the No. 1 ranking until he was 40.

Day remains No. 1 in the world at the moment, but there is a new flavor of the moment in the sport and his name is Dustin Johnson, winner of the U.S. Open and the WGC-Bridgestone in consecutive appearances entering this week. A win by Johnson, who’s No. 2 now, at Troon would elevate him to No. 1 in the world.

What’s the deal? Why can no one sustain?

“It’s mostly mental,” Spieth said. “I know right now at this present moment, I’ll be brutally honest with you, it’s not the same feeling I had when I was getting ready for the Open Championship last year. Yeah, it’s hard to keep it. It puts a light on what Tiger has done even more so.”

While Spieth, who has fallen to No. 3 in the rankings, conceded to having lost at least a little bit of the grip on his 2015 mojo, he also takes offense to the notion he, McIlroy or Day have fallen off very dramatically.

“You say these runs; I mean, no one’s really gone off on a run,” Spieth said. “Everyone goes through peaks and valleys. If you’re calling [this] a valley … I’ve still won twice and second in a major [this year]. If that’s a valley, then that’s going to be a lot of fun when we get back up to a peak. [I] will stress to you that we hope the word ‘run’ is not used. I don’t want this to be a run. I want this to be the norm.”

McIlroy’s dander becomes raised slightly at the notion he has fallen off some sort of map of the game’s top stars.

One British columnist recently wrote he is in danger of becoming the Ringo Starr of the current Fab Four, in reference to the perceived least-regarded of The Beatles.

“Probably the first time I’ve been compared to The Beatles,” McIlroy said. “I mean, those guys [Spieth, Day and Johnson] are having a great run at the minute. I can’t worry about other guys. If I focus on myself and make sure I’m playing the best that I can, I’m pretty confident that if I go out and play my best golf I’m going to win more times than not.”

Then came this velvet-hammer subliminal message from McIlroy: “I’ve got four major championships, and I’d love to add to that tally, just as those guys would love to add to their one or two majors that they have and just keep going.”

McIlroy, of course, has four majors, Spieth two and Day and Johnson one.